Ars System Guide special: it’s easy being green

Ars goes in a new direction in this month's System Guide as we offer …

Drawing power

In years past, 60 percent or 70 percent efficiency from an ATX power supply was the standard. A system with a processor, motherboard, memory, video card, and hard drive that sucked 100W of DC power meant that the then-typical 60 percent efficient PSU was drawing almost 167W from the wall. That extra 67W ended up as waste heat that had to be exhausted from the power supply, lest it heat up the rest of the computer.

Since 2005, power supplies certified under the 80 PLUS standard have made finding a higher-efficiency (80 percent or better) unit much easier, by giving increased efficiency a unified banner and marketing label. 100W consumed by the components inside the PC with an 80 percent efficient PSU means only 125W from the wall, which in turn means less waste heat and less energy being wasted away, with the added bonus of having to run the air conditioner less for users in the tropics or other already hot areas.

A typical high-efficiency unit today is typically at least 83 percent efficient, with some units aiming for 85 percent or better. Green PC builders, or even any system builder, should have no problem finding 80+ percent efficient units, thanks to 80 PLUS' extensive power supply list. An efficient PSU of note for a low-power desktop system is the PicoPSU, which runs very cool and looks great, until you remember it sucks power from an external +12v power brick. Its seemingly incredible efficiency isn't quite as incredible once the power brick's efficiency is factored in—think about 85~87 percent, which is still superb.

Most nicer PSUs are RoHS friendly by this point, and some, such as Sparkle/Fortron-Source, proudly advertise such facts on their web site. Sparkle/Fortron-Source also has a Green power supply line (their GLN and HLN series), emphasizing high efficiency and reduced materials use with smaller heatsinks. Most important, these designs seem to work just fine, as demonstrated in reviews.

For green builders, a high-efficiency rating is the primary thing to look for in a power supply, alongside clean power output and reliability. Low noise is also nice, but is not an absolute necessity.

The most obvious thing that many system builders tend to forget is to appropriately size the power supply. A low-power system for light use probably won't break 155W from the PSU, even with a power-hungry Pentium D 820, according to SilentPCReview. Most power supplies today have fairly flat efficiency curves instead of the drastic efficiency drop-offs at very low and very high loads, so speccing a PSU that is too large generally does not extract a huge efficiency penalty. It does waste both money and materials, though—a system with only 155W of DC load is going to need less beefy transistors, capacitors, heatsinks, and the like inside its PSU, so buying an appropriately sized PSU is more environmentally friendly than a massively oversized unit that won't ever be used at more than 25 percent or 35 percent of capacity.

Sound and Ethernet are integrated into the motherboard and chipset-level RAID is already included (and rarely used in such a box), so there's not a lot to see here.

An environmentally friendly gaming box will probably get by fine without add-in cards as well. Integrated sound may not be as nice as a good discrete card from Creative, Auzentech, or M-Audio, but it works and performs fine for the most part. NVIDIA's recent purchase of Ageia, the leading physics card maker, means discrete physics cards will probably remain (thankfully) dead to gamers, and Bigfoot Network's KillerNIC had even less penetration than AGEIA's PhysX PPU, which means it was and is even less significant.

Optical drives generally sit idle and draw only a trickle of power, so we won't worry about them. Scouring the forums shows 1W to 3W for most and even less for laptop drives. Peak load may be an issue, but that's so infrequent in most cases we're not going to worry about it. Frequently-used CDs and DVDs can always be ISOed to the hard drive and mounted virtually, generating further power savings.

Monitors and peripherals

Avoid these too

Speakers, keyboards, mice, card readers, and other peripherals draw almost nothing when not in use, even with that annoying bright blue standby LED on some products. Pinching the last watt may make sense in some cases, in which case hitting the off switch on your speakers and monitor isn't that hard.

Monitors are the big one here. A newer LCD draws 40-60W maximum in a modest 19", 20", or 22" size. That number grows close to 85W or 100W maximum for a 24" unit. Drop them down to standby or turn them off entirely when not using them to minimize power consumption. By comparison, a 21" CRT typically uses more than 120W, more than double the power of a typical 22" LCD.